The present invention relates generally to intersomatic implants which can be used in the surgical treatment of the spine.
A great many intersomatic implants are already known. These include, in particular, implants made up of several parts, particularly to give the implants certain deformability characteristics. These known implants have the disadvantage of being more expensive and difficult to manufacture, and more awkward to fit. These implants can also suffer from long-term reliability problems.
In order to overcome some of the above-mentioned disadvantages, certain implants are provided in the form of one-piece hollow bodies, or cages, having roughened areas on their upper and lower faces in order to ensure good initial immobilization relative to the overlying and underlying vertebral plates. The hollow bodies permit bone to grow through the implant for fusing the implant to vertebral bone. One such implant having a hollow body is disclosed in FR-A-2,703,580.
These known one-piece implants, despite the presence of roughened areas which become anchored in the vertebral plates, may suffer from inadequate stability in some cases. This is because the quality of the anchoring, which is effected by a simple translational movement, depends on the hardness of the bones.
Other implants have an outer body and an inner anchorage reinforcement element that is screwed into the outer body. The threads of the anchorage reinforcement element project above and below the upper and lower faces of the outer body.
One object of the present invention is to improve this type of known implant.